1. Field of the Invention
The present invention relates to a jig and a method for processing a cylinder block for used in finish processing for a cylinder bore in the cylinder block.
2. Related Art
For example, in a cylinder block making up of an engine installed on an automobile or the like, aperture portions requiring a predetermined roundness are formed. As these aperture portions, for example, a cylinder bore, which slidably incorporates a piston connected to a crankshaft of the engine via a con rod or the like, and a bearing hole, which supports a journal portion of the crankshaft and so on. In other words, a finish processing (a perfect circle processing) such as honing process is performed, for the aperture portions such as the cylinder bore and the bearing hole, so as to acquire the predetermined roundness.
Meanwhile, the roundness of the aperture portion such as the cylinder bore is affected by bolt fastening accompanying the assembly of components on the process of assembling the engine or the like. In other words, the cylinder block or the like is distorted (deformed) due to a tightening force of the bolt fastening (a fastening axial force), and the roundness of the aperture portion such as the cylinder bore is deteriorated, by assembling the components into the cylinder block by the bolt fastening.
Consequently, conventionally, the finish processing is performed in the state that the distortion (the deformation) caused by assembling the components into the cylinder block or the like is reproduced (simulated) for the aperture portion such as the cylinder bore (see, for example, JP 2004-243514 and JP 2002-120107).
JP 2004-243514 shows a dummy head processing, as a representative example of method for performing the finish processing in the state that the distortion accompanying the assembly of the components into the cylinder block is preliminary added to the aperture portion such as the cylinder bore. In the dummy head processing, so-called a dummy head is used. The dummy head is a jig for processing different from the cylinder head incorporated as an actual product, and is assembled into the cylinder block using the fastening means such as the bolt (the head bolt) as with the cylinder head. In other words, the distortion caused by assembling the cylinder head into the cylinder block is added to the aperture portion such as the cylinder bore, by assembling the dummy head into the cylinder block. In the circumstances, the finish processing is performed in the aperture portion such as the cylinder bore. Accordingly, the effect of the actual assembly of the cylinder head on the roundness of the aperture portion such as the cylinder bore (the deterioration of the roundness) is reduced.
The above-mentioned dummy head processing includes the following problems. The dummy head processing is based on the concept of performing the finish processing for the aperture portion such as the cylinder bore, in the state that the assembly completed condition as an engine assembly is reproduced, by assembling the dummy head into the cylinder block with the bolt fastening. For this reason, the preparation for a considerable number of dummy heads considering a production cycle time, the equipments for assembling/removing the dummy head or the like are required. Therefore, the preparation for a considerable number of dummy heads and additional spaces as well as the additional equipments and process for assembling/removing the dummy head, for processing the cylinder block with the dummy head processing are required, compared to the processing of the cylinder block in a normal processing without the dummy head processing, thereby increasing the production cost.
Meanwhile, JP 2002-120107 discloses a technology of the roundness processing for the bearing hole (the journal bearing hole) supporting the crankshaft. For example, as shown in the specification, the bearing hole is formed by means of assembling a lower case to the cylinder block by the bolt fastening.
JP 2002-120107 discloses a technology for performing the roundness processing of the bearing hole, in the state that the deformation equivalent to one caused by the bolt fastening or the like is added, by adding a prescribed load using a pressing pin, instead of the bolt fastening, so as to form the bearing hole. The technology is aimed at improving the production efficiency by getting rid of the bolt fastening process and the bolt demolition process, in the roundness processing for the bearing hole.
The technology disclosed in JP 2002-120107 is used in the processing for the bearing hole, but has a possibility of application to the processing for the cylinder bore. In this case, specifically, the deformation is added to the cylinder bore, by adding the predetermined load to the cylinder head mounting surface by the pressing pin, instead of assembling the dummy head into the cylinder block by the bolt fastening. Accordingly, the dummy head is not needed, whereby the problems on the dummy head processing caused by using the dummy head as described above are solved.
However, the deformation of the cylinder bore caused by assembling the cylinder head (the dummy head) into the cylinder block is caused not only by the pressing on the cylinder head mounting surface but also by the action of the fastening axial force by the bolt fastening (the tensile force by the bolt). For this reason, the deformation of the cylinder bore caused by assembling the cylinder head become difficult to be fully reproduced, by using the technology disclosed in JP 2002-120107.
In this respect, it is an object of the present invention to provide a jig and a method for processing the cylinder block, which is capable of using existing equipments for preliminary adding the cylinder bore to the predetermined deformation and which is capable of improving the production efficiency, without increase in the space, the equipment, the process or the like leading to the increase of the production cost, in the finish processing for the cylinder bore in the cylinder block.